Rails5 fix specs duplicate key value violates unique constraint…

What does this MR do?

Fix broken specs for Rails 5 that load gpg signatures. I can't locally reproduce the error, but these :js fixes the problem and also makes sense since these page now performs async js calls to load gpg signature.

Broken specs:

spec/features/projects/files/user_replaces_files_spec.rb:{26,52}
spec/features/projects/files/user_edits_files_spec.rb:{58,75,94,115}
spec/features/projects/files/user_deletes_files_spec.rb:{24,44}
spec/features/projects/blobs/shortcuts_blob_spec.rb:{19,27}
spec/features/projects/files/user_browses_files_spec.rb:220

See previous scheduled Rails 5 pipeline: https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/87940083, https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/87941099, https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/87939500, https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/87939633, https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/87941235

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides